Direct Analysis for Cocaine in Urine by High-Performance Liquid Chromatography (HPLC) Using a Column-Switching Technique

The analysis of urine for the presence of drugs generally requires that the drug be first extracted from relatively large concentrations of endogenous compounds. By replacing the injection loop with a loop incorporating a cyano precolumn, urine can be injected directly onto the high-performance liquid chromatograph. Interfering compounds are washed off of the precolumn, with the valve in the load position. When the valve is then switched to inject, the mobile phase elutes the cocaine from the precolumn onto the analytical column. A preliminary identification of cocaine and benzoylecgonine can be made using this technique, which requires 100 μL of sample and has a detection limit of 10 ng/mL.